CO2 capture in combined cycles with air-blown gasification of pre-dried high-moisture lignite

This paper deals with the energy impact of pre-combustion CO2 capture in air-blown IGCC plants when gasifying pre-dried high-moisture lignite. An original in-house code, integrated with Aspen Plus, was used to carry out the thermodynamic IGCC assessment, which points out that a significant lignite pre-drying is necessary for higher efficiency. Considering a residual moisture in the pre-dried lignite ranging from 10 to 30 wt%, HHV efficiency presents a decreasing trend, with a maximum value slightly less than 37% for 90% of CO2 avoided, even though the higher the residual moisture in the pre-dried lignite, the lower the extraction of steam from the bottoming cycle of the IGCC plant for the water-gas shift reaction. However, introducing the specific primary energy consumption for CO2 avoided (SPECCA) as an index for the energy cost related to CO2 capture, reductions seem to be possible when gasifying pre-dried lignite with higher residual moisture. In particular, a SPECCA value as low as 2.79 MJ/kgCO2 has been calculated for the case with the highest (30 wt%) residual moisture in the lignite. Ultimately, measures for energy saving at the CO2 capture and storage plant are investigated as well.